On-Board Diagnostics is a computer-based system originally designed to reduce emissions by monitoring the performance of major engine components. A basic OBD system consists of an ECU (Electronic Control Unit), which uses input from various sensors (e.g. oxygen sensors) to control the actuators (e.g, fuel injectors) to get the desired performance. The “Check Engine” light, also known as the MIL (Malfunction Indicator Light), provides an early warning of malfunctions to the vehicle owner. A modern vehicle can support hundreds of parameters, which can be accessed via the DLC (Diagnostic Link Connector) using a device called a scan tool.
In the first part of the thesis I expound the details of tasks, then I describe the On-Board Diagnostic systems, their progression and function. I show some OBD scan tools, and I design a multipurpose diagnostic hardware module based on the acquired experience. I go through the hardware design steps, starting with the specification, show the selected components. I describe the circuit diagram and printed circuit board design. Then I describe the workflow of assembly and the testing phase. Finally, I discuss the possibilities of further development, summarize and evaluate the performed work.